<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body >
    <div style="width: 100px; height: 100px; font-size: 10px;">     <!--必须要有初始值-->
        点击bebigger
    </div>
    <script>
        let elm=document.querySelector('div')
        // elm.style.width=100
        // elm.style.height=200
        elm.onclick=function()
        {
            alert("hh")
            let sum=parseInt(elm.style.fontSize)
            sum+=10;
            elm.style.fontSize=sum+'px'
        }
    </script>
</body>
</html>